Digital Processing - Dalsa Piranha 3 Series User Manual

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ad ju stm ent, follow ed by an analog offset ad ju stm ent. These ad ju stm ents are applied to
the vid eo analog signal prior to its d igitization by an A/ D converter.
The d igital processing chain contains the FPN correction, the PRN U correction, the
backgrou nd su btract, and the d igital gain and offset. All of t hese elem ents are u ser
program m able.
Figure 13: Signal Processing Chain
Analog Processing
Optim izing offset perform ance and gain in the analog d om ain allow s you to achieve a
better signal-to-noise ratio and d ynam ic range than you w ou ld achieve by trying to
optim ize the offset in the d igital d om ain. As a resu lt, perform all analog ad ju stm ents prior
to any d igital ad ju stm ents.
1. Analog gain (
2. The analog offset (

Digital Processing

To optim ize cam era perform ance, d igital signal processing shou ld be com pleted after any
analog ad ju stm ents.
1. Fixed pattern noise (FPN ) calibration (calcu lated u sing the
2. The d igital offset (
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or com m and ) is m u ltiplied by the analog signal to increase the
signal strength before the A/ D conversion. It is u sed to take ad vantage of the fu ll
d ynam ic range of the A/ D converter. For exam ple, in a low light situ ation the
brightest part of the im age m ay be consistently com ing in at only 50% of the DN . An
analog gain of 6 d B (2x) w ill ensu re fu ll u se of the d ynam ic range of the A/ D
converter. Of cou rse the noise is also increased .
sao cao
or
introd u ced into the vid eo path to ensu re that the A/ D is fu nctioning properly. The
analog offset shou ld be set so that it is at least 3 tim es the rm s noise valu e at the
cu rrent gain.
su btract aw ay ind ivid u al pixel d ark cu rrent.
com m and ) enables the su btraction of the ―artificial‖ A/ D offset
sdo
(the analog offset) so that application of the PRN U coefficient d oesn't resu lt in
artifacts at low light levels d u e to the offset valu e. You m ay w ant to set the
if you are not u sing FPN correction bu t w ant to perform PRN U correction.
com m and ) or black level is an ―artificial‖ offset
Piranha 3 User Manual
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com m and ) is u sed to
sdo
valu e
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